The fossil of one of the biggest ants ever has been discovered in Wyoming. Over fifty milliion years ago, it crossed the arctic to get there. Scientists have analyzed the data, and believe that a hot planet fosters the spread of super-sized ants.

It's funny how size affects the way people think of things. An adorably small hippo would make an unsettlingly large cat. And that lovable little pipsqueak, the hummingbird, would be a hideous monster if instead of a bird it was an ant. Bad news. At one time - it was an ant. Like a hummingbird, this ancient ant had wings and could fly. It was about two inches long, and spread to Wyoming from Europe, through the arctic.

To be fair, the continents were different shapes and in different places than they are now, so going from Europe to America wasn't the difficult journey it later became. But no matter the duration of the journey, it required heat. The world was a hotter place in the past, and for some reason, 'hot' means 'giant ants'. Researchers believe that the earth was heated by bursts of greenhouse gasses throughout this period, and the heat that generated gave the ants the climate they needed to go through the arctic. Once they'd walked the land bridge between continents, the ants spread down through what would become North America. Impressions in rocks are all that remain of these ants, but that doesn't mean people can breathe easy. When researchers mapped out the habitat of large ants, past and present, they found that they were always associated with warm temperatures. No one is sure why, but if the planet heats up too much, future researchers may get a look at the reason for this enlargement in real time.